GB2242205A

GB2242205A - Driving needles bar of a tufting machine

Info

Publication number: GB2242205A
Application number: GB9105150A
Authority: GB
Inventors: Bernard Brear; Alan Beckett
Original assignee: TUFTEX Ltd
Current assignee: TUFTEX Ltd
Priority date: 1990-03-22
Filing date: 1991-03-12
Publication date: 1991-09-25
Also published as: GB9105150D0

Abstract

The needle bar 10 of a tufting machine has its linear movement controlled by an electronically-controlled motor, possibly a stepper motor, via a rack-and-pinion mechanism, or a carriage slidably mounted on a low friction track, or a cam, preferably a uniform linear displacement conjugate cam. <IMAGE>

Description

LINEAR MOVEMENT CONTROL APPARATUS This invention relates to apparatus for imparting intermittent linear movement to a machine member.

More particularly, the invention is concerned with apparatus for intermittently and linearly displacing a sliding machine member, forwards or backwards, through a selected distance, referred to hereinafter as "the pitch".

It is an object of the present invention to provide a linear movement control apparatus which is accurate and in which any pitch discrepancy is non-accumulative.

According to a first aspect of the present invention a linear control apparatus for a sliding machine member comprises an electronically-controlled motor operatively coupled to the sliding machine member through the intermediary of means for converting rotary motion to linear motion.

According to this invention a second aspect of the present is a linear movement control apparatus comprising an electronically controlled motor drivingly coupled to the sliding machine member through the intermediary of a rack-and-pinion mechanism.

According to a third aspect of the present invention a linear movement control apparatus for a sliding machine member comprises an electronically-controlled stepper motor operatively coupled to the sliding machine member.

Preferably, the stepper motor drive is transmitted to the sliding machine member by a carriage, preferably mounted for reciprocable movement on a low friction track.

Preferably, a connecting link couples the carriage to the sliding machine member.

The term "stepper motors used herein and in the claims is to be construed as including a servomotor or a reduction motor.

According to a fourth aspect of the present invention, an electronically controlled motor is drivingly connected to the sliding machine member by a cam, preferably a uniform linear displacement conjugate cam, to impart the required linear movement to the sliding machine member.

The linear movement control apparatus has particular but not exclusive application to carpet tufting machines.

As is known to those skilled in the art, a pattern is produced in a carpet tufting machine by introducing face yarns of different colours set in the tufting machine widthwise in zones of repeat pattern. Additionally, the needle bar of the tufting machine is caused to move in a predetermined manner and, as a result of these two functions, a discrete and repeatable pattern for a carpet is produced.

The linear movement control apparatus of the present invention is applied, in a carpet tufting machine, to the needle bar.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying diagrammatic drawings, in which: - Fig. 1 illustrates diagrammatically a first linear movement control apparatus according to this invention; Figs. 2 and 3 are respectively a front view and plan view of the linear movement control apparatus of Fig. 1; Fig. 4 illustrates the main drive shaft of a carpet tufting machine; Fig. 5 illustrates diagrammatically a stepper motor/carriage linear movement control apparatus; Fig. 6 illustrates diagrammatically a motor/cam linear movement control apparatus; and Fig. 7 illustrates the main drive shaft of a carpet tufting machine.

In the following description the sliding machine member is the needle bar of a carpet tufting machine.

The needle bar 10 is connected to a sliding drive bar 11 carried in a framework 12 comprises parallel plates 13, 13A and 13B connected in spatial relationship by bolts 14 and sleeves 15.

Between the plates 13. 13A are mounted parallel guide members 16, 17 between which the sliding drive bar 11 moves.

The sliding drive bar 11 is connected to a rack 18 which is driven by a sprocket 19 mounted on the output shaft 20 of a reduction gear box 21 driven by an electronically controlled motor 22.

The revolutions of the latter to give the required linear displacement of the needle bar 10 are controlled by an encoder or resolver 23 mounted on the motor 22.

In order to obtain the correct timing of the needle bar 10 and the tufting machine the motor 22 is switched on at a set time related to the position of the tufting machine shaft 24 relative to bottom dead centre and the angle a (see Fig. 4).

The angle a is determined by the value of N.S. and N.C. as hereinafter defined.

The bottom dead centre position and the switching time are monitored by an encoder or resolver 25 mounted on the machine shaft 24. This also monitors the tufting machine speed, and should this speed exceed a predetermined value for the required pitch, the motor 22 is not switched on until the speed has been corrected. The encoder or resolver 25 is set to monitor the bottom dead centre of the needle bar stroke via a sensor 26.

The linear movement control apparatus of the present invention is designed to give a number of basic pitches as required and, merely by way of example, such basic pitches, in a carpet tufting machine, may be between 0.100" and 0.187" with an accuracy of displacement of the order of +/- 0.0005".

With the present invention any variance in the pitch movement, which is monitored, will be corrected upon the next movement of the needle bar 10.

In Fig. 5, the needle bar 30 of a carpet tufting machine has its linear reciprocating movement imparted to it by a sliding carriage 31 connected to the needle bar 30 by a connecting link 32. As the needle bar 30 moves not only sideways but also up-and-down, the connecting link 32 between the sliding carriage 31 preferably comprises a slideway permitting bi-directional movement. The carriage 31 is mounted on a low friction track 33 and is driven by a stepper motor 34 via a timing belt 35. The stepper motor 34 is electronically controlled by a programmable controller 36 having an associated keypad.

The programmable controller 36 holds a multiplicity of programmes within its memory, a minimum of sixteen programmes preferably, any one of which can be called up when required. A keypad is used to enter new programmes and to vary new or existing programmes to give desired repeatable patterns.

The timing and synchronising of the linear movement control apparatus to the carpet tufting machine is achieved by means of an encoder or resolver 37 mounted on the main drive shaft 38 of the machine, and set to monitor via a sensor 39 the bottom dead centre of the needle bar stroke (see Fig. 7).

By measuring the angle 1800 - aO, from the bottom dead centre position the start of needle bar sideways movement will be defined. This will be accurate regardless of the machine speed.

The time available to move the needle bar 10 must, of course, be linked to the fastest tufting machine speed, but it may be possible to link to the actual tufting machine speed when the tufting machine is running slower than maximum. This would have an advantage by allowing extra time to complete the sliding needle bar movement and thus reducing the thrust applied thereto, which preferably should not exceed 80kg.

The time available to move the needle bar 10 is governed by two factors.

1) The machine speed.

2) The ratio (see Fig. 6) between N.S. and N.C., N.S.

being the total needle stroke and N.C. the distance by which the needle clears the backing material.

The carpet tufting machine speed must be monitored and if the set maximum speed is exceeded the machine must be slowed down or stopped.

The linear movement control apparatus of the present invention is almost entirely electronically controlled, the main mechanical parts being the needle bar 10 or 30 and the sliding drive bar 11 or carriage 31 respectively. The reduction in mechanical parts in the tufting machine will result in low friction and reduced forces.

Reference is now made to Fig. 6.

In this embodiment the needle bar 40 is coupled to a uniform linear displacement conjugate cam 41 driven by an electronically controlled motor 42 via a reduction gear box 43.

The revolutions of the motor 42 to give the required angular displacement of the cam 41 are monitored by means of an encoder or resolver 44 mounted on the motor 42.

In order to obtain the correct timing of the cam 41 and the tufting machine the motor 42 is switched on at a set time related to the machine shaft position relative to bottom dead centre and the angle (see Fig. 7).

The angle cx is determined by the value of N.S. and N.C.

The bottom dead centre position and the switching time are monitored by the encoder or resolver 37 mounted on the machine shaft 38. This also monitors the machine speed, and should this speed exceed a predetermined value for the required pitch, the motor 42 is not switched on until the speed has been corrected.

Claims

1. A linear control apparatus for a sliding machine member comprises an electronically-controlled motor operatively coupled to the sliding machine member through the intermediary of means for converting rotary motion to linear motion.

2. A linear movement control apparatus comprises an electronically controlled motor drivingly coupled to the sliding machine member through the intermediary of a rack-and-pinion mechanism.

3. Apparatus as claimed in claim 2, in which the sliding machine member is connected to a sliding drive bar movable between parallel guides and connected to the rack of the rack-and-pinion mechanism.

4. Apparatus as claimed in claim 3, in which the rack is driven by the sprocket which is mounted on the output shaft of a reduction gear driven by the electronically-controlled motor.

5. Apparatus as claimed in claim 4, in which the electronicallycontrolled motor is controlled by an encoder or resolver.

6. A linear movement control apparatus for a sliding machine member comprising an electronically-controlled stepper motor operatively coupled to the sliding machine member.

7. Apparatus as claimed in claim 6, in which the stepper motor drive is transmitted to the sliding machine member by a carriage, preferably mounted for reciprocable movement on a low friction track.

8. Apparatus as claimed in claim 7, in which a connecting link couples the carriage to the sliding machine member.

9. A linear movement control apparatus in which an electronically controlled motor is drivingly connected to the sliding machine member by a cam, preferably a uniform linear displacement conjugate cam, to impart the required linear movement to the sliding machine member.

10. A linear movement control apparatus, substantially as hereinbefore described with reference to Figs. 1 to 4 or Figs. 5 and 7 or Figs. 6 and 7 of the accompanying drawings.

11. A tufting machine incorporating a linear control apparatus as claimed in any one of claims 1 to 10, and in which the sliding machine member is the needle bar of the tufting machine.